1. Field of the Invention
The present invention relates to a coated optical fiber to be used, for example, in light communication and particularly relates to a coated optical fiber having a colored layer provided thereon.
2. Background Information
In an optical fiber to be used for light communication, it is considered preferable to provide a plastic coating (primary coating) on the outer circumference of a fiber immediately after the fiber is formed, regardless of the kind of the fiber, whether it is an optical glass fiber or a quartz glass fiber. Such a coating protects the fiber from injuries caused to the fiber surface which may occur when the fiber is formed, or, by the growth of cracks generated on a naked fiber when it is exposed to the air. For such a plastic layer, thermosetting silicon resin, ultraviolet setting resin (hereinafter referred to "UV resin"), or radiation setting resin, are some of the coatings most normally found in the art. UV resin has recently found wide acceptance.
An optical fiber having a primary coating layer of UV resin is manufactured, for example, through a process in which UV resin is continuously applied, by use of coating dyes, onto an optical fiber which is wiredrawn, by use of a wiredrawing furnace, and irradiated with ultraviolet rays to thereby harden the UV resin. One or more optical fibers coated with UV resin are further coated with a secondary coating layer such that a coated optical fiber is produced. For the purpose of discrimination, sometimes, an individual UV resin coated fiber is coated with a colored layer as a secondary coating layer. This optical fiber is referred to as a color-coated optical fiber.
Generally, a plurality of such color-coated optical fibers are put side by side, and a bundle coating is applied onto the outside of the color-coated optical fibers to thereby form a tape-like coated optical fiber.
In the case where the tape-like coated optical fibers are to be joined to each other at the time of laying a cable or the like, it is necessary to remove the bundle coating layers at the respective end portions of the respective optical fibers so as to expose the color-coated optical fibers. However, when the bundle coating layers are removed, the colored layers are often removed together with the bundle coating layers. If these colored layers are simultaneously removed, it becomes impossible to discriminate each of the coated optical fibers from one another, making the subsequent joining of the coated optical fibers extremely difficult and time consuming.